If you are using Hipchat from Atlassain for work or projec chat then the install guide for Linux is made for Ubuntu.
Only problem if you are using another distribution based on Ubuntu like Linux Mint 18.3 Cinnamon then it will fail to install.
The original guide looks like this
The problem is that the repository that the install guide will generate is wrong and not existing.
Just replace $(lsb_release -c -s) with xenial like this
sudo sh -c 'echo "deb https://atlassian.artifactoryonline.com/atlassian/hipchat-apt-client xenial main" > /etc/apt/sources.list.d/atlassian-hipchat4.list' wget -O - https://atlassian.artifactoryonline.com/atlassian/api/gpg/key/public | sudo apt-key add - sudo apt-get update sudo apt-get install hipchat4
That will match with the Ubuntu 16.04 branch that Linux Mint 18.3 is based on.
If you allready have done the damage using the guide from Atlassain then just edit the file with
sudo nano /etc/apt/sources.list.d/atlassian-hipchat4.list
And find the sylvia line, replace it with xenial so it looks like this
deb https://atlassian.artifactoryonline.com/atlassian/hipchat-apt-client xenial main
sudo apt update sudo apt install hipchat4